Multi-application transponder circuits for contactless electronic identification and/or access systems are already known. WO Patent Nos. 97/34265 and 02/35464 for example disclose solutions where the memory space of the transponder circuit is segmented into a plurality of memory segments for each receiving data relating to a determined application from among a plurality of distinct applications. WO Patent No. 97/34265 offers a solution where the segmentation of memory space is carried out as a function of the quantity of data to be stored, each memory segment having a variable length. Headings are also available for identifying each of the memory segments and their allocation to the application concerned. WO Patent No. 02/35464 has a solution adopting a more rigid organisation of the memory space available in the transponder circuit, a plurality of memory segments being predefined to each receive data relating to a determined application from among a plurality of distinct applications. With respect to the solution disclosed in WO Patent No. 97/34265, this solution offers the advantage of simplifying, to a very large extent, addressing of the memory words and the memory read and write operations. This solution, however, has the drawback of a non-upgradeable and not very flexible memory structure.
One constraint of transponder circuits for contactless electronic identification and/or access systems lies in the relatively limited resources that it is possible or that one could consider incorporating therein. It is in particular desirable to propose inexpensive solutions to implement, which do not weigh too heavily on the manufacturing costs of the transponder circuit. High capacity memories and developed file systems, as encountered particularly in the field of computer science, are unfortunately not suited for use in transponder circuits of the aforementioned type, not only because of the implementation costs thereof, but also because of the high calculation power required to operate such solutions. Moreover, in the case of transponder circuits of the passive type where the energy necessary to power these circuits is directly derived from a low frequency electromagnetic field (typically 125 kHz) produced by the associated interrogation device, the low working frequency is not suited to implementation of a developed memory architecture, since the latter is too demanding in terms of processing time.
It is thus desirable to propose a multi-application transponder circuit whose memory architecture offers more flexibility than the prior solutions having a rigid memory organisation like that disclosed in WO Patent No. 02/35464 while taking care not to over-burden or make the memory architecture too complex. It is an object of the present invention to offer such a solution.